Avg

AvgAggregate 实现平均聚合。

类定义

    public static class AvgAggregate implements Aggregate<Number>
    {
        public void initialize(Number val) 
        {
            sum = val.doubleValue();
            count = 1;
        }
 
        public void accumulate(Number val) 
        {
            sum += val.doubleValue();
            count += 1;
        }
         
        public Object result() 
        {
            return new Double(sum/count);
        }
         
        public void merge(Aggregate<Number> other) 
        {
            AvgAggregate otherAvg = (AvgAggregate)other;
            sum += otherAvg.sum;
            count += otherAvg.count;
        }
 
        double sum;
        long count;
    }